What must be ensured regarding the mask for infant use with portable oxygen?

The correct response is based on the fact that infants require a specific type of oxygen delivery that does not overwhelm their delicate respiratory systems. A low-flow mask is ideal for infants using portable oxygen because it delivers a controlled amount of oxygen at a lower rate, which is crucial for their safety and comfort.

Using a low-flow mask ensures that the infant receives the necessary supplemental oxygen without the risk of delivering too much oxygen, which could lead to complications such as oxygen toxicity. This approach allows for a gentle supply of oxygen to accommodate the infant's needs while preventing potential harm from excessive flow.

Other options, such as a high-flow mask, would not be appropriate, as they could provide too much oxygen or pressure, which can be detrimental to infants. Similarly, having a backup supply may not be a necessity regarding the mask itself; instead, it relates to the overall oxygen delivery system. A disposable requirement after one use may be more relevant for hygiene purposes but does not directly address the design and function of the mask for an infant.